The Nano-Virus is a microscopic microbiological NanotechnologicalNanorobot (or Nanobot) with the ability to replicate itself. It was accidentally released from a laboratory, and now humans are trying to shut it down by broadcasting a "kill-code" that will deactivate the virus. This means that "cure research" (or in this case "kill code broadcast") starts from the beginning of the game. Like all other normal plague types, one must kill all of humanity before the cure, or in this case code, can be transmitted.

To compensate for the fact that the kill-code broadcast begins immediately after a starting country is chosen, the Nano-Virus has higher than average starting infectivity, better resistance to all climates (except humid ones, where it has a larger penalty instead), cheaper symptom costs, and symptoms that slow development of the cure which can be evolved for free.

The most effective strategy is one that relies on widespread transmission in a short amount of time, which makes the Nano-Virus ideal for speed run strategies. The abilities of this plague type are mostly ones that slow down and pull back the "cure"(with two notable exceptions). Therefore, by purchasing these abilities at the beginning of the game, the player can neutralize the cure disadvantage and use the infectivity, climate resistance, and cheaper symptoms to their advantage. Moreover, players should not worry about their nano-virus being detected, because every country gives maximum priority to the kill-code broadcast from the beginning, so even if it is detected, it doesn't make as much of a difference. Countries, however, will still close their airports and seaports. Please see Nano-Virus Strategy Guides for more strategies.